1. Field of the Invention
The present invention relates to an image forming apparatus such as a copying machine, printer, facsimile machine, and digital multifunctional device, and more particularly to improvement of a paper folding apparatus which is used as a finisher and the like of the image forming apparatus.
2. Description of the Related Art
There has been conventionally known a paper folding apparatus which has a function of forming any fold line at any position on a sheet of paper such as a copier paper, recording paper, and printing paper ejected from an image forming apparatus of an electrophotographic system such as a copying machine, printer, and facsimile machine. For example, in an electrophotographic copying machine for copying a large-size draft such as a draft of a drawing, the draft is usually copied on large-sized coping paper such as A0 or A1 paper. Keeping or handling these large-sized copier papers as they are takes up a lot of storage space, or causes inconvenience in handling, thus the papers are usually folded and stored. However, folding these copying papers by hand generally requires a considerable amount of time, and sometimes folding the papers takes several times longer than copying. For this reason, there has been developed a paper folding apparatus which is disposed at a ejection path of a copying machine, and there has been known a paper folding apparatus for folding an A0 sized drawing into an A4 size.
In the case of folding large-size paper into small-size paper using such a paper folding apparatus, when filing the folded paper in a file or the like, the edge of the paper is also filed. Also, it may be necessary to change a starting position for folding the edge due to limitations of the image information on the paper. In order to prevent such folding of edges or to form a most appropriate fold line corresponding to the image on the paper, it is necessary for an operator to fold the edges of the folded paper again by hand, and then file the paper by means of a staple or paper punch to create a file. However, the burden on the operator is increased if folding of the edges is manually performed on every single piece of paper. Therefore, there is proposed an edge folding device which can automatically fold in the edges of paper and reduce the burden placed on the operator.
For example, Japanese Patent Application No. 2849914 discloses a technology in a paper folding apparatus in which at least a pair of rotating members which are driven in mutual synchronization are provided along a paper conveying path, and a groove and a protrusion for forming a fold line on paper are provided in the rotating members respectively. In this conventional technology, however, since each of the rotating members rotates, slips a sheet of paper therebetween, and thereby form a fold line, and papers are stacked along the fold lines thereof into a paper storage portion provided below each of the rotating members, the problem is that it is difficult form a fold line nicely.
Further, Japanese Patent Application No. 3173121, for example, discloses an edge folding device which comprises paper conveying means for conveying paper, edge fold-in means having an edge folding member capable of vertical movement between a first position in which an edge of the paper is scooped up and a second position in which the edge of the scooped paper is folded in, paper detecting means for detecting an arrival of the paper in the vicinity of the edge folding member, edge fold controlling means for controlling so as to set the edge folding member at a constant timing after arrival the paper is detected by the paper detecting means, set the edge folding member in the second position at a constant timing after an edge of the paper is loaded on edge folding member, and fold in the edge of the paper under the second position, and edge fold-up means having a pair of fold rollers for nipping the paper whose edge is folded in and folding the edge upward. However, as described above, the position for starting to fold the edge is determined according to the shape of the edge folding member which is capable of vertical movement of scooping up the fold line formed on the folded edge, thus a user cannot change the position for starting to fold the edge at the leading edge of the paper, even if he wants to for the reason of filing or of the image information on the paper. There was no way but to replace the folding member with the one having a different shape in order to change the position for starting to fold the edge.
Furthermore, Japan Registration of Utility Model No. 2524155 discloses a technology for using and end section folding member to fold upward an end section of paper conveyed by paper conveying means, and forming a fold line on the end section of the paper by inserting a curved part of the folded-up paper into a nip portion of a pair of rollers. In this conventional technology, however, although the end portion of the is folded up by the end section folding member which is capable of vertical movement of scooping up an end section of paper, the curved part of the folded up paper is inserted in the nip portion of the pair of rollers, thus inserting into the nip portion was difficult, the angle of the fold line fluctuates, and the paper is bent due to wrinkles generated on the paper.